1. Field of the Invention
This invention relates generally to downhole cutting tools and clean-out methods and more particularly, but not by way of limitation, it relates to a downhole rotary cutting tool that has both a grinding and a liquid jetting capability.
2. Description of the Prior Art
The prior art has seen a number of different downhole tools of the rotary type that may be used for cutting casing, underreaming, notching formations and other downhole operations. However, Applicant is not aware of any type of rotary tool that has the capability for both an abrading rotary action and a lateral high pressure jet action such as that provided by the present invention. Such a tool is particularly useful in downhole operations where it is desired to remove a section of casing, e.g., a twenty or so foot casing section, while simultaneously removing surrounding cement or earthen formation by means of liquid jet pressure. Such a subterranean configuration is useful in adapting an existing cased borehole for accommodation of a horizontal drill string extension and continued horizontal drilling. The invention is an improvement on the downhole tool teachings of U.S. Pat. Nos. 5,201,817 and 5,242,017.